These plugins you’re trying to use are VST effects. I assume that you’re trying to use them with a real guitar.
You’ll have to use an Audio Track for that. Using the Inspector (the panel to the left), you can select the guitar audio input channel and apply your VST effects as Inserts.
Instrument Tracks are for virtual VST instruments. You can pick them using the panel to the right. Cubase LE comes with a bunch of free ones.